Sucker rod coupling with zinc inserts



Jan. 1, 1946. Y J, F, EATON y2,392,033

SUGKER- ROD GOUPLING WITH ZINC INsERTs Filed NOV. l, 1941 Patented Jan.1,1946

SUCKER ROD COUPLING WITH ZINC l A l t INSERTS John F. Eaton, Tulsa,Okla., assignor to Bethlehem Steel Company, a corporation of Pennsylvania Application November 1, 1941, Serial No. 417,422

(Cl. 21M-197) 4 Claims.

This invention relates to an improvement in sucker rod joints, and moreparticularly to a protective coupling guide for use under electrolytlcconditions in oil wells.

Four methods of producing oil from wells are today in use: natural iiow,artificial flow induced b foil or gas lift, swabbing and pumping. But pping is certainly the method most widely utllized, and the pumps areusually actuated by a string of sucker rods. The success of deep oilwell pumping, in particular, is largely dependent upon the length ofservice received from sucker rods, for rod 4breaks arey costly in labor,down time, and replacements.

Standard sucker rods, made according to American Petroleum Institutespecifications, are highgrade steel rods from 5A; inch to 1V; inch innominal diameter and 25 to 30 feet in length overall, including thecoupling if any. Pony rods are similar, but shorter. Bothsucker and ponyrods are characterized 'by an'enlarged or upset portion at each end,which at one end at least terminates in an externally threaded pin.

The box and pin type of sucker rod has an interiorly threaded end or boxat the opposite end from the pin, which dispenses with the use ofcouplings to make connections, but the double pin type, exteriorlythreaded at .both ends', employs couplings and subcouplings to make up astring of sucker rods. These last are short internally hereto'f ore beenused in such wells, but' these steels are not only rather high-priced,even in normal times, but are now practically unobtainable due toshortages. Since iron and zinc form a galvanc couple, zinc dissolving,and iron remaining unaffected, galvanizing is a good protectant againstelectrolysis, but galvanized rods and couplings are fairly expensivealso, and inA dynamic tests the soft zinc coating has been found toresist abrasive wearvery poorly and to facilitate the formation ofsurface nicks or notches which concentrate operating stresses andproduce proy gressive cracks and breaks ending in costly lishthreadedmembers screwed onto the pins, being called couplings i-f both ends arethreaded alike and subcouplingsif the ends are threaded differently, asin joining rods of different sizes for the tapered strings of deepwells.

The advantage of using the double pin type of rodis that all abrasionagainst the side of the tubing is taken on the coupling, so that thecoupling rather than the much more expensive sucker rod receives thewear. Couplings can thus be removed and are usually renewed severaltimes during the life of the rods, for the failure of a I coupling'would obviously entail the same considerable expense as the breakage .ofa sucker rod.

Electrolysis is provably the main cause of sucker rod and couplingfailure in some fields, as in certain West Texas wells where about '75per cent of the rod breaks are due to electrolytic action. Brlnesimpregnated with hydrogen sulphide gas, shown by the familiar test fordiscoloration or v.blackening of lead acetate paper and found in manyoil bearing horizons, have a highly destructive electrolytic pittingeffect upon sucker rods or the like of ordinary steels.

Special corrosion resistant alloy steels have ing jobs. Moreover,detached flakes of the zinc coating which have dropped to the bottom ofthe well will tend to hang between the ball and seat ofthe traveling orstanding 4valves of thepump, thereby breaking the fluid seal, ifadequate provision is not made for prevention. And for long life of thecouplings and well tubing, the couplings should be extremely hard andhighly polished on their outer surface, which is impossible withgalvanizing.

To utilize this principle'of the selective corros ion of zinc in contactwith iron, withoutpermitting undue abrasive weakening of the couplingsor rods, is one object of my invention.

Another object is a sucker rod coupling of high resistance to attack byelectrolysis.

A further object is a guide or coupling which will protectv the adjacentsucker rods from electrolytic action.

Still another object is a coupling which is provided with inexpensive,self-cleaning and readily renewable zinc inserts.

Other objects, advantages and purposes of my linvention will hereinafterappear in the following pages of the specification and claims.

Having thus given a general description of the advantages of myinvention, I shall now in order to make the same more clear refer to theannexed sheet of drawings forming a. part of this specification and inwhich like characters of reference indicate like parts.

Figure 1 is a side elevation of the coupling shown connecting two suckerrods within the well tubing;

Fig. 2 is a longitudinal section of the coupling which more clearlyshows the zinc inserts and sucker rod pins;

Fig. 3 is a, transverse sectional view taken substantially on the line3-3 of Fig. 1, showing the wrench flats on the coupling and the topsucker rod pin;

Fig. 4 is a transverse sectional view taken cates the well tubing, 2identical sucker rods,

and 3 the coupling joining said sucker rods. Each sucker rod 2 isprovided with a slender rod or bar portion 4, a head 5, a wrenchengaging square 6, pin shoulder "I, and externally threaded pin 8. Atboth ends of coupl'ng 3 is an internally threaded box portion 9 adaptedto engage the externally threaded pink8. Milled flats` I supply meansfor wrench engagement and the enlarged middle body portion I I isprovided with a longitudinally bored central chamber I2, connecting saidbox portions 9, and with vertically fluted elongated slots I3. Withinsaid chamber I2 are vertically arranged several spool-shaped zincinserts I4 each provided with a circumferential groove I5.

The zinc inserts I4 are placed within `the chamber I2 at the time ofmaking up the sucker rod string, sufficient open space being left in thechamber I2 above zinc inserts I4 to permit a limited amount of freevertical movementfto said inserts. For illustration the coupling hasbeen shown as equipped with five (5) zinc inserts, but it will bereadily understood that this number is not critical and `may be variedas. de-

sired to accord with the size of coupling used and other operatingconditions. The number loosen and knock off the corrosion products as.soon as they form, maintaining thu: the prior as a joint for pony rods,equally as well.

In other respects also, although I have shown and described my inventionin considerable detail, Iv do not wishto be limited strictly to theexact and specificv details shown and described.

' but may use such substitutions, modifications or equivalents thereofas are embraced within the scope of the invention or as are pointed outin the claims. Having thus described my invention, what I claim Vas newand desire to secure by Letters Patent is:

`1 ,A couplingfor sucker rods pumping corrosive well fluid comprisingend box portions and of zinc inserted 'couplings required willvary alsowith the concentration of electrolyte in the particular well, but one toevery 50 or 60 feet of ex posed rod, i. e., at every other joint. willusually be found ample to protect both the rods and the other couplings.

Besides guarding the zinc inserts I4 froml abrasion against the tubingI, the enlarged'body portion II serves to hold the rods in the center ofthe tubing during the pumping stroke Iand lessens the chance ofbuckling.

If the zinc inserts I4 were permittedto become coated with corrosionproducts theywould lose a great part 'of their effectiveness incomhating corrosion within a short time. But in operation most of thewell fluid flowing past the moving coupling passes -through the fluidpassage slots I3 and is directed against the surface of the zinc insertsI4. Thegrooves I5 in said inserts increase the surface -friction of thefluid passing the inserts, with the effect of lifting and agitating theinserts; and the fact of a plurality of small inserts instead of onelarge one further adds to the agitation and movement of the inserts inthe coupling. The resultof the continuous vibration and impact shocks isto a vertically slotted central'chambercontaining a plurality of looselymovable spool-shaped zinc inserts having fluid-engagingv grooves soplaced that the fluid strikes them 'while moving In the directionoftheir long axes.v

2. A coupling for sucker rods comprising end box portions, an. enlargedhollow longitudinally pierced portion perforated to permit the passageof fluid vertically, and within said hollow pierced portion a pluralityof vertically disposed superposed movable cylindrical zinc inserts eachhaving in the middle `a circumferential groove to frictionally engagesaid fluid.A

3. A coupling for sucker rods for ,use in corrosive wellfluids,comprising a hollow steel shell `internally threaded at both endsto `engage vmovable'coupling section located intermediate adjacentlengths of sucker rods and consisting ofY an enlarged perforated outersteel shelll with `exterior diameter slightly less than the interiordiameter of the tubing. and a plurality of movable selectivelycorrodible metallic spools therein.

. JOHN F. EATON.

